Counting and indicating mechanism



Oct. 6, 1959 5, RAPPAPQRT- 2,907,523

COUNTING AND INDICATING MECHANISM Filed May 17, 1957 V 3 Sheets-Sheet l IN VENTOR Szy/wandiapp agar? ATTORNEY Oct. 6, 1959 s. RAPPAPORT 2,907,523

COUNTING AND INDICATING MECHANISM Filed May 17, 1957 3 Sheets-Sheet 2 gbuxcnwssnks mmwmdlzmm Q Nk h o 5 73 l 46 ZNVENTOR 5/74 4' Sag/wand Fez 9,0 4;: art

32 9 A ATTORNEY United States Patent COUNTING AND INDICATING MECHANISM Sigmund Rappaport, Port Washington, N.Y., assignor t0 Sperry Rand Corporation, Ford Instrument Company Division, Long Island City, N.Y., a corporation of Delaware Application May 17, 1957, Serial No. 659,872 13 Claims. ((31. 235-125) This invention relates to mechanical counters which are especially adapted for use on airplanes for continuously indicating the longitude or latitude thereof throughout its flight.

Various types of mechanical counters have been developed for this purpose most of which comprise a plurality of numerically calibrated drums, having two side by side sets of numerals running in opposite directions thereon, which drums are driven intermittently, one from the other, and a mask which is automatically shifted back and forth between two positions when the 0 and the 180 meridians are crossed. The mask which may be a cylinder that encloses all of the drums or a segment of a cylinder which only covers a portion of the drums, is provided with two sets of staggered side by side windows through one of which one set of numerals may be seen when a plane is traveling in west longitude, and through the other of which windows the other set of numerals may be seen when a plane is traveling in east longitude. One type of prior counter employs four drums and a mask. The first or minute drum is provided with two side by side rows of numerals, from 0 to 9, one of which runs clockwise and the other of which runs counterclockwise. The second drum indicates minute intervals and is provided with two rows of numerals running from O to 5, one clockwise and the other counterclockwise, and is driven step by step by the first or minute drum, being advanced one digit for each revolution of the minute drum. The third drum is driven by the second drum and is provided with two side by side rows of numerals running from 0 to 9 clockwise and the other counterclockwise; and the fourth drum is driven by the third drum and is provided with two side by side rows of numerals running from 0 to 170 in intervals of ten, one clockwise and the other counterclockwise.

Another type of prior counter is very similar to the above type but instead of each drum being provided with two rows of side by side numerals running in opposite directions each drum is divided into two side by side drums on one of which the numerals run clockwise and on the other of which the numerals run counterclockwise.

Counters of the aforesaid types have certain inherent shortcomings in that the speed is limited due to the number of intermittent drives and the inertia of the drums and the mask. Also during the intermittent movement of successive drums the numerals appear staggered making reading unpleasant, and due to their geometry and mode of display a half minute is lost or gained during each mask transfer, which error however is not accumulative.

It is therefore the principal object of this invention to provide a mechanical counter of the aforesaid type in' which the inherent shortcoming of prior counters are eliminated.

In accomplishing this I reduce the number of intermittently driven drums and I eliminate the mask. In accordance with my invention I provide the two axially aligned side by side drums and a sprocket. The first or unit drum has two side by side rows of numerals thereon, one row being calibrated from 0 to 9 in a clockwise direction and the other being calibrated from 0 to 9 in a counterclockwise direction. The second or tens drum is 2,907,523 Patented Oct. 6, 1959 likewise provided with two side by side rows of numerals, one row being calibrated from O to 5 in a clockwise direction and the other being calibrated from 0 to 5 in a counterclockwise direction. These two drums are operative to indicate minutes of east or west longitude from 00' to 59, the two clockwise rows indicating minutes of west longitude and the two counterclockwise rows indicating east longitude.

For indicating degrees of longitude I provide an endless tape of thin flexible material which is calibrated in one direction in a continuous sequence from E 000 to E 179 for indicating degrees of east longitude, and in the opposite direction from W 000 to W 179 for indicating the degree of west longitude. The tape is provided with two sets of alternate opaque and transparent strips, one set of which is disposed along side the east calibrations and the other set of which is disposed along side the west calibrations. Each set is composed of two opaque strips and two transparent strips, with a transparent strip being disposed adjacent the east calibrations and an opaque strip being disposed adjacent the west calibrations. The transparent strips beside the east calibrations align with the opaque strips beside the West calibrations, and the transparent strips beside the west calibrations align with the opaque strips beside the east calibrations. The tape is also provided along one edge thereof with a row of perforations which are adapted to be engaged by the teeth or" the sprocket to advance the tape in one direction or the other in accordance with the direction of rotation of the sprocket. The tape encompasses at least 270 of the drums and sprocket with two of the tour strips being disposed over the unit drum and the other two strips being disposed over the tens drum. When the counter is indicating west longitude transparent strips will be disposed over the clockwise rows of numerals on the unit and tens drums so that the numerals thereunt er may be visible, and the opaque strips will be disposed over the counterclockwise rows of numerals so that they will be hidden from View; and when the counter is indicating east longitude transparent strips will be disposed over the counterclockwise rows of numerals so that they will be visible, and opaque strips will be disposed over the clockwise rows of numerals so that they will be hidden from view.

The construction of the counter is such that when a plane is traveling from east to west in east longitude the degrees of east longitude being indicated by the counter will progressively increase, and after the plane crosses the 180 meridian into west longitude the degrees of west longitude being indicated by the counter will progressively decrease. And conversely if a plane is flying from west to east in east longitude the degrees of east longitude being indicated by the counter will progressively decrease, and after the plane crosses the 0 meridian into west longitude the degrees of west longitude being indicated by the counter will progressively increase.

The unit drum is driven either continuously or intermittently by a computer in accordance with the ground speed and the angle the planes path makes with the meridian which values are imparted to the computer. The rate at which the unit drum is driven will be proportional to the product of the planes ground speed the sine of the angle between the planes path and the meridian. When the plane is flying from east to west the unit drum will be driven clockwise by the computer, and when the plane is flying from west to east the unit drum will be driven counterclockwise. After each revolution thereof the unit drum will advance the tens drum one digit, and after each revolution of the tens drum it will advance the tape one digit.

The length of the tape, carrying 366 numerals as heretofore described, is therefore determined by the height of the numerals. For a numeral height of five thirtysecond of an inch the length of the tape would therefore be approximately sixty inches, and the winding, unwinding and storing of this length of tape may cause some difficulties. However, this length can be reduced by 50% if a strip of tape is calibrated on both sides and the ends therefor connected together after the tape has been twisted through a half turn of 180 to form the well known so called Moebius strip. And for further ease of winding, unwinding and storing the tape may be given a plurality of odd number half turns before securing the ends together.

When the tape is twisted a half turn, or a plurality of odd number half turns, before the ends thereof are secured together to form the Moebius strip which is the preferred manner of use, it must be calibrated on both sides. On one side of the tape the calibrations are disposed adjacent one edge of the tape and progressively increase from E 000 to E 179 downwardly from the top of the tape; and on the other side of the tape the calibrations are disposed adjacent the opposite edge of the tape and progressively increase from W 000 to W 179 upwardly from the bottom of the tape. The alternate transparent and opaque strips are disposed between the two rows of calibrations and extend from end to end of the tape. When the tape is twisted a half turn and the two ;ends thereof secured together the lower ends of the transparent strips will align with the upper ends of the opaque strips. Also in this formthe tape is perforated along both edges thereof.

Having stated the principal object of the invention other and more limited bjects thereof will be apparent from the following specification and the accompanying drawings forming a part thereof in which:

Fig. l is a plan view of a longitude counter and indicator, constructed in accordance with my invention, in dicating the longitude of a plane traveling from east to west on which the counter is mounted, just before the plane passes from east to west longitude;

Fig. 2 is a view similar to Fig. 1 in which the longitude of a plane just after it has passed from east longitude to west longitude is indicated;

Fig. 3 is a fragmentary plan view of one form of counter with the cover removed showing the unit and tens drums and the sprocket by which the degree tape is advanced;

Fig. 4 is a development of the unit drum showing the calibrations thereon;

Fig. 5 is a development of the tens drum showing the calibrations thereon;

Fig. 6 is a development of the endless tape, used with the form of counter shown in Fig. 3, showing the construction and calibration thereof; 7

Fig. 7 is a view similar to Fig. 3 showing the tape of Fig. 6 applied to the drums and sprocket of Fig. 3;

Fig. 8 is a vertical transverse sectional view through the counter of Figs. 1 to 7, the plane of the section being indicated by the line 88 on Fig. 7;

Fig. 9 is a face view of one-side of a length of tape, before it is twisted a half turn and the ends secured together to form a Moebius strip of tape, showing the construction and calibration of that side thereof;

Fig. 10 is a view similar to Fig. 9 of the other side of the tape of Fig. 9;

Fig. 11 is a diagrammatic view illustrating the manner in which the tape of Figs. 9 and 10 is twisted a half turn and ends secured together in to a Moebius strip;

Fig. 12 is a fragmentary face view of one side of the tape of Figs. 9 and 10 showing the manner in which the ends of the tape, after twisting, are secured together and how the calibrations of Fig. 9 line up and register with the calibrations of Fig. 10; I

Fig. 13 is a view similar to Fig. 12 looking at the face of the tape directly behind that shown in Fig. 12;

Fig. 14 is a view similar to Fig. 3 showing the arrangetude counter and indicator, constructed according to my invention, which comprises a base 2 having a pair of spaced similar brackets 3, secured thereto and extending upwardly therefrom, by and between which a horizontally disposed shaft 4 is supported. Rotatably mounted upon the shaft 3 are a unit drum 5, a tens drum 6 and a sprocket drum 7 which is provided with a row of equally spaced teeth 8 adjacent one side thereof. The unit drum 5 has two side by side rows of numerals 9 and 11 thereon. The row 9 runs clockwise from 0 to 9 in an increasing sequence, and the row 16 runs counterclockwise in a decreasing sequenceQas more clearly shown in Fig. 4. The tens drum 6 has two side by side rows of numerals 11 and 12 thereon, one of which, 11, runs clockwise from 0 to 5 in an increasing sequence, and the other of which, 12, runs counterclockwise from O to 5 in a decreasing sequence, as more clearly shown in Fig. 5. The drums 5 and 6 in conjunction with each other are adapted to count and indicate minutes of longitude from 0 to 59.

For counting and indicating degrees of longitude 1 provide an endless tape 15 of any suitable flexible material. The tape 15 is calibrated throughout the length thereof, adjacent one edge, in one direction on the tape in an increasing sequence from E 000 to E 179 as indicated at 16 in Fig. 6, and in the opposite direction on the tape in an increasing sequence from W 000 to W 179 as indicated at 17 in Fig. 6. By-reference toFig. 6 it will be seen that the entire length of the tape 15 is calibrated on the outer surface thereof, with E 000 and W 090 contiguous and E 179 and W 179 contiguous. The E calibrations are adapted to indicate degrees of east longitude and the W calibrations are adapted to indicate degrees of west longitude. The tape 15 isprovided with a row of equally spaced apertures 18 between the'calibrationsl6-17 and the edge 19 thereof; and between the calibrations 1617 and the opposite edge 20 thereof the tape is provided with two sets 21 and 22 of alternate transparent and opaque strips running lengthwise of the tape parallel to the calibrations 16-17. The set 21 which is alongside the east calibration 16 consists of the transparent strips 23 and 24 and the alternate opaque strips 25 and 26 with the transparent strip 23 being adjacent the east calibrations 16. And the set 22 which is alongside the west calibrations 17 consists of the opaque strips 27 and 28 and the alternate transparent strips 29 and 30 with the opaque strips 27 being adjacent the west calibrations. By further reference to Fig. 6 it will be seen that the transparent strips 23 and 24-of the set 21 align with the opaque strips 27 and 28 of the set 22, and that the opaque strips 25 and 26 of the set 21 align with-the transparent strips 29 and 30 of the set 22, each set of strips extending froma medial line31 between E 000 and W 000 to a medial line 32 between E 179 and W 179. 1 As shown in Figs. 3, 7 and 8 the tape 15 is dispose over and around the greater part of the unit drum 5, the tens drum 6 and the sprocket drum 7 with the teeth 8 ofthe sprocket drum 7 engaging in the apertures 18 of the tape 15; and with the aligned strips 2630 and 24- 28 overlying the two rows of numerals 9 and 10 respectively on the unit drum 5, and the aligned strips 2549 and 23-27overlyingthe two rows of numerals 11 and 12 respectively on the tens drum 6. A pair of idler rollers 33 and 34, carried by and between the brackets 3, are provided to maintain the tape 15 in contact with the drums 5,6 and 7 as the tape is withdrawn, by the sprocket V drum 7, from and returned to a suitable chamber or reprovided with a long narrow window 37 through which the longitude being indicated may be read as will be explained hereinafter.

In operation the unit drum 5 is driven, either continuously or intermittently by a computer (not shown) through a shaft 38 and a pair of meshing gears 39 and 40, one of which 39 is connected to the shaft 38 and the other of which 40 is connected to the drum 5, At the completion of each revolution thereof the unit drum 5 advances the tens drum 6 one digit in the same direction of rotation as the drum 5; and at the completion of each revolution thereof the tens drum 6 rotates the sprocket drum 7' in the same direction a sufiicient amount to advance the tape 15 one digit. The mechanism by which the tens drum 6 is rotated by the unit drum 5, and the sprocket drum 7 is rotated by the tens drum 6 may be disposed within the drums 5, 6 and 7 and is indicated by the numeral 38 in Fig. 3. This mechanism 38 may be any one of several different types such as are used in counters having a plurality of axially aligned drums which are successively intermittently rotated one from the other. It may be of the mutilated gear type such as shown in U.S. Patents No. 1,439,097 or No. 2,661,903 or it may be a modified Geneva drive. And since this mechanism is merely a matter of choice and per se forms no part of the present invention it is not believed necessary to show and describe it in detail herein.

The operation of the counter constituting the invention will now be described assuming that it is mounted upon an airplane travelling from east to west in east longitude. The drum 5 will be rotated clockwise as viewed in Fig. 8 by an actuating computer (not shown) at a speed which is proportional to the product of the ground speed of the airplane and the sine of the angle of its path with the meridian, which values are imparted to the actuating computer. in east longitude the opaque strips 25 and 26 will cover the rows of numerals 9 and 11 on the drums 5 and 6 and hide them from view; and the transparent strips '23 and 24 are over the rows and 12 of numerals on the drums 5 and 6 which will therefore be visible. The minutes of east longitude will therefore always be indicated by the rows 10 and 32 of numerals on the drum Sand 6 regardless of which direction the plane is traveling and the degrees of east longitude will likewise always be indicated by the E calibrations on the tape 15, which may be read through the window 37 in the cover 36. The E degree calibrations on the tape 15 and the minute calibrations on the drums 5 and 6 viewed through the window 37 will progressively increase until the plane crosses the 180 meridian, at which time transparent E strips 23 and 24 will be advanced from over the rows of numerals 10 and 12 and the opaque W strips 27 and 28 will be advanced into position over the rows of numerals 10 and 12 hiding them from View, and at the same time the opaque E strips 25 and 26 will be advanced from over the rows of numerals 9 and 11 and the transparent W strips moved into position over the rows of numerals S and 11 on the drums 5 and 6 exposing them to view. The minutes of west longitude will always be indicated by the rows of humerals 9 and 11 on the drums 5 and 6 and the degrees of west longitude will always be indicated by the W calibrations regardless of the direction the plane is traveling. As the plane continues traveling from east to west in west longitude the degrees and minutes of west longitude being indicated will progressively decrease until the plane crosses the 0 meridian. But if the plane is traveling from west to east in east longitude the drums 5, 6 and 7 will be rotated counterclockwise by the actuating computer. The degrees and minutes of east longitude being indicated will therefore progressively decrease until the plane crosses the 0 meridian into west longitude, after which the degrees of west longitude being indicated will progressively increase as the plane continues traveling toward the east.

In Figs. 9 to 15 I have shown a slightly modified form of the invention in which the length of tape required is reduced by 50% by twisting it a half turn and then securing the ends thereof together forming the so called Moebius strip. In forming a tape of this character I select a piece of material 40 of the proper width and length and place the east longitude calibrations 41 on one side thereof and the west longitude calibrations 42 on the other side thereof. For east longitude I calibrate one side 43 of the iece 49 from E 001 to E 179 from end to end adjacent one edge 44 thereof in one direction; and for west longitude I calibrate the opposite side 45 of the piece 4% from W 000 to W 179 adjacent the opposite edge 46 thereof in a direction opposite to the east calibration 41, with the calibration E 000 preceding the calibration W 000. Between the two rows of calibrations 41 and 42. I provide the strip 40 with two transparent strips .7 and 43 and two alternately arranged opaque strips 4? and 50, all of which extend from end to end of the piece 40, with the transparent strip 47 adjacent the east calibration 41 and the opaque strip 50 adjacent the west calibrations 42, all as shown in Figs. 9 and 10. And along each of the edges 44 and I provide a row of equally spaced perforations as shown at 51 and 52. On the side 43 of the piece 40 adjacent E 000 and E 179 I provide blank portions 53 and 54 respectively which are adapted to overlie and abut each other after the piece 40 has been twisted a half turn, as diagrammatically shown in Fig. 11, and the ends secured together, as shown in Figs. 12 and 13, into an endless ta e 55. When the ends are secured together the ends of the transparent strips 47 and 48 will register with the ends of the opaque strips 49 and 50 as is also clearly shown in Figs. 12 and 13.

When the tape 55 as shown in Figs. 9 to 13 is used I provide the mechanism with an idler drum 56 adjacent the unit drum 5, as shown in Fig. 14, to support the width of tape overhanging the unit drum 5. Otherwise the construction and arrangement of the unit drum 5, the tens drum 6, the sprocket drum 7 and the means for rotating them are the same as that shown in Figs. 1 to 3 and 7 and 8. In use the tape 55 is disposed over and around the drums 5, 6, 7 and 56, as shown in Figs. 14 and 15, and as the tape 55 is advanced by the sprocket drum 7 in either direction first the sides 43 and 45 are alternately uppermost, and the position of the edges 44 and 46 alternately reversed and exposed to view through the window 37 in the cover 36, as is characteristic of the so called Moebius strip. When the counter 1 is indicating east longitude the side 43 with the E calibrations thereon will be uppermost with the transparent strips 47 and 43 over the rows of numerals 12 and 10 respectively, on the unit and tens drums 5 and 6, exposing them to view, and the opaque strips 49 and 50 will be over the rows of numerals 11 and 9 respectively, on the drums 5 and 6, hiding them from view; and when indicating west longitude the side 45 with the W calibrations thereon will be uppermost and the rows of numerals 10 and 12 will be hidden from view by the opaque strips 49 and S0, and the rows of numerals 9 and 11 will be exposed to view through the transparent strips 47 and 48. Otherwise the operation of the counter 1, when using the tape 55, will be exactly the same as that described in connection with the use of the tape 15.

From the foregoing it will be apparent to those skilled in this art that I have provided a very simple and efi'icient mechanism for continuously counting and indicating the longitude of a plane traveling from east to west, or west to east, in either east or West longitude.

Although the counter and indicator of the invention has been shown and described in connection with the continuous counting and indicating the longitude of a travel ing airplane, it can be equally well adapted for counting and indicating latitude by merely calibrating the tape 15 and/or 55 in degrees of north and south latitude instead of east and west longitude. Also the mechanism may be used equally well for indicating the longitude or latitude of a ship or other mobile vehicle as well as an airplane. i

It is to be understood that I am not limited to the specific construction shown and described herein as various modifications may be made therein within the spirit of the invention and the scope of the appended claims. For instance, if desired, the tens drum 6 may be dispensed with in which case the unit drum 5 would be provided with two side by side rows of numerals extending in opposite directions from O to 59, and only one transparent strip and one opaque strip would be provided on the tape 15 or 55.

I claim:

1. A counting and indicating mechanism of the character described comprising a drum and a sprocket rotaably mounted in axial alignment, an endless flexible tape overlying said drum and said sprocket and extending around a substantial portion of the peripheries thereof, said drum being provided with two side by side rows of graduations one of which extends in one direction for indicating minutes of east longitude and the other of which extends in the opposite direction for indicating minutes of west longitude, said tape being calibrated in one direction for indicating degrees of east longitude and in the opposite direction for indicating degrees of west longitude, and said tape being provided with two spaced elongated transparent sections disposed parallel to said calibrations, one of which overlies said row of graduations extending in said one direction on said drum when said counting and indicating mechanism is indicating east longitude and the other of which overlies said row of graduations extending in said opposite direction on said drum when said counting and indicating mechanism is indicating west longitude, means through which said drum is rotated in either direction and means by which said sprocket is intermittently rotated by said drum to thereby advance said tape step by step from one calibration to the next succeeding calibration.

2. A counting and indicating mechanism of the character described comprising a unit drum, a tens drum and a sprocket rotatably mounted in axial alignment. an endless flexible tape overlying said drums and said sprocket and extending around a substantial portion of the peripheries thereof, said unit drum being provided with two side by side rows of numerals one of which progressively increased from 0 to 9 in a clockwise direction and the other of which progressively increases from 0 to 9 in a counterclockwise direction, and said tens drum being provided with two side by side rows of numerals one of which progressively increases from 0 to in a clockwise direction and the other of which progressively increases from 0 to 5 in a counterclockwise direction, said unit and said tens drums being adapted to indicate minutes of east or west longitude, said tape being calibrated from E 000 to E 179 in one direction and from W 000 to W 179 in the opposite direction for indicating degrees of east or west longitude, and being provided with alternate elongated transparent and opaque sections extending parallel to said-calibrations, said transparent sections being adapted to overlie one row of numerals on each of said unit and tens drums when said counter .is indicating degrees and minutes of east longitude and to overlie the other row of numerals on each of said unit and tens drums when said counter is indicating degrees and minutes of west longitude, means through which said unit drum is rotated, means by which said tens drum is intermittently rotated by said unit drum, and means by which said sprocket is intermittently rotated by said me'ans is selectively rotated in either direction, means means overlying said drum means and controlled by the movement of said tape by which said set of graduations adapted for indicating minutes of west longitude are hidden from view when said mechanism is indicating east longitude and said set of graduations adapted for indicating east longitude are hidden from view when said mechanism is indicating west longitude.

4. A counting and indicating mechanism as defined in claim 3 in which said endless tape is provided with a half twist whereby the opposed faces thereof will be alternately uppermost and exposed to view as said tape is advanced by said sprocket.

5. A counting and indicating mechanism of the character described comprising a rotatably mounted drum means, a sprocket rotatably mounted in axial alignment with said drum means, means through which said drum means is selectively rotated in either direction, means by which said sprocket is rotated by said drum means, an endless flexible tape disposed about said sprocket and adapted to be advanced step by step by the intermittent rotation of said sprocket, said drum means being provided with two sets of graduations one of which is adapted for indicating minutes of east longitude and the other or" which is adapted for indicating minutes of west longitude, said tape being'calibrated throughout the length thereof for indicating degrees of east and west longitude in conjunction with said drum means, and means carried by said tape and overlying said drum means by which said set of graduations adapted for indicating minutes of west longitude are hidden from view when said mechanism is indicating east longitude and said set of graduations adapted for indicating east longitude are hidden from view when said mechanism is indicating west longitude.

6. A counting and indicating mechanism as defined in claim 5 in which said, endless tape is provided with a half twist whereby the opposed faces thereof will be alternately uppermost and exposed to view as said tape is advanced by said sprocket.

7. A counting and indicating mechanism as defined in claim 5 in which said last-mentioned means comprises a longitudinally extending narrow opaque section on said tape and a longitudinally extending narrow transparent section disposed between said opaque section and said calibrations on said tape for indicating degrees of east longitude, a second narrow longitudinally extending transparent section on said tape and a second longitudinally extending opaque section disposed between said second transparent section and the said calibrations on said tape for indicating degrees of west longitude, said first transparent section being disposed in alignment with said second opaque section and said first opaque section being disposed in alignment with said second transparent section.

8. A counting and indicating mechanism of the character described comprising a rotatably mounted drum means, a sprocket rotatably mounted in axial alignment with said drum means, means through which said drum means is selectively rotated in either direction, means by which said sprocket is intermittently rotated by said drum means, an endless flexible tape disposed about said sprocket and adapted to be advanced step by step by the intermittent rotation of said sprocket, said drum means being provided with two sets of graduations one of which is adapted for indicating minutes of east longitude and the other of which is adapted for indicating minutes of west longitude, said endless tape being provided on one face thereof with calibrations extending in one direction for indicating degrees of east longitude and on the opposed face thereof with calibrations extending in the opposite direction for indicating degrees of west longitude, and said endless tape having a half twist therein whereby the opposed faces thereof will be alternately uppermost and exposed to view as said tape is advanced by said sprocket, and means overlying said drum means and controlled by the movement of said tape by which said set of graduations adapted for indicating minutes of west longitude are hidden from view when said mechanism is indicating east longitude and said set of graduations adapted for indicating east longitude are hidden from view when said mechanism is indicating West longitude.

9. A counting and indicating mechanism of the character described comprising a rotatably mounted drum means, a sprocket rotatably mounted in axial alignment with said drum means, means through which said drum means is selectively rotated in either direction, means by which said sprocket is intermittently rotated by said drum means, an endless flexible tape disposed about said sprocket and adapted to be advanced step by step by the intermittent rotation of said sprocket, said drum means being provided with two sets of graduations one of which is adapted for indicating minutes of east longitude and the other of which is adapted for indicating minutes of west longitude, said endless tape being provided on one face thereof with calibrations extending in one direction for indicating degrees of east longitude and on the opposed face thereof with calibrations extending in the opposite direction for indicating degrees of west longitude, and said endless tape having a halt twist therein whereby the opposed faces thereof will be alternately uppermost and exposed to view as said tape is advanced by said sprocket, and means carried by said tape and overlying said drum means by which said set of graduations adapted for indicating minutes of west longitude are hidden from View when said mechanism is indicating east longitude and said set of graduations adapted for indicating east longitude are hidden from view when said mechanism is indicating west longitude.

10. A counting and indicating mechanism as defined in claim 9 in which said last-mentioned means comprises a longitudinally extending narrow opaque section on said tape and a longitudinally extending narrow transparent section disposed between said opaque section and said calibrations on said tape for indicating degrees of east longitude, a second narrow longitudinally extending transparent section on said tape and a second longitudinally extending opaque section disposed between said second transparent section and the said calibrations on said tape for indicating degrees of west longitude, said first transparent section being disposed in alignment with said second opaque section and said first opaque section being disposed in alignment with said second transparent section.

11. A counting and indicating mechanism of the character described comprising a unit drum, a tens drum, and a sprocket rotatably mounted in axial alignment, means through which said unit drum is selectively rotated in either direction, means by which said tens drum is intermittently rotated by said unit drum, means by which said sprocket is intermittently rotated by said tens drum, an endless flexible tape disposed about said sprocket and adapted to be advanced step by step by said sprocket, said unit drum being provided with two side by side rows of graduations one of which progressively increases from to 9 in one direction and the other row of which progressively increases from O to 9 in the opposite direction, said tens drum being provided with two side by side rows of graduations one of which progressively increases from 0 to in one direction and the other row of which progressively increases from O to 5 in the opposite direction, said unit drum and said tens drum being adapted for indicating minutes of east or west longitude, said endless tape being provided on one face thereof with calibrations extending in one direction for indicating degrees of east longitude and on the opposed face thereof with calibrations extending in the opposite direction for indicating degrees of west longitude, and said endless tape having a half twist therein whereby the opposed faces thereof will be alternately uppermost and exposed to view as said tape is advanced by said sprocket, and means overlying said drums and controlled by the movement of said tape by which said rows of graduations extending in said one direction on said unit and tens drums are hidden from view when said mechanism is indicating east longitude and said rows of graduation extending in the said opposite direction on said unit and tens drums are hidden from view when said mechanism indicating west longitude.

12. A counting and indicating mechanism of the character described comprising a unit drum, a tens drum, and a sprocket rotatably mounted in axial alignment, means through which said unit drum is selectively rotated in either direction, means by which said tens drum is intermittently rotated by said unit drum, means by which said sprocket is intermittently rotated by said tens drum, an endless flexible tape disposed about said sprocket and adapted to be advanced step by step by said sprocket, said unit drum being provided with two side by side rows of graduations one of which progressively increases from 0 to 9 in one direction and the other row of which progressively increases from O to 9 in the opposite direction, said tens drum being provided with two side by side rows of graduations one of which progressively increases from 0 to 5 in one direction and the other row of which progressively increases from 0 to 5 in the opposite direction, said unit drum and said tens drum being adapted for indicating minutes of east or west longitude, said endless tape being provided on one face thereof with calibrations extending in one direction for indicating degrees of east longitude and on the opposed face thereof with calibrations extending in the opposite direction for indicating degrees of west longitude, and said endless tape having a half twist therein whereby the opposed faces thereof will be alternately uppermost and exposed to view as said tape is advanced by said sprocket, and means carried by said tape and overlying said unit and tens drums by which said rows of graduations extending in said one direction on said unit and tens drums are hidden from view when said mechanism is indicating east longitude and said rows of graduation extending in the said opposite direction on said unit and tens drums are hidden from view when said mechanism is indicating west longitude.

13. A counting and indicating mechanism as defined in claim 12 in which said last-mentioned means comprises a longitudindly extending narrow transparent section disposed between said opaque section and said calibrations on said tape for indicating degrees of east longitude, a second narrow longitudinally extending transparent section on said tape and a second longitudinally ex tending opaque section disposed between said second transparent section and the said calibrations on said tape for indicating degrees of West longitude, said first transparent section being disposed in alignment with said second opaque section and said first opaque section being disposed in alignment with said second transparent section.

References Cited in the file of this patent UNITED STATES PATENTS 

